In burning buildings the rapid spread of fire, the burning through of doors, and the fast decrease of the structural load bearing capacity of steel pillars, beams, metal structures and the like cause the most frequent and the heaviest damage from the fire.
One of the main requirements of fire-retardant materials is the best possible heat insulating ability. The objective of such materials is to inhibit the flow of heat towards the part of the building or the building structure to be protected as effectively as possible. The role of fire inhibiting materials is a ual one with regard to its function.
By their heat insulating capacity fire inhibiting materials installed as layers into fire inhibiting structures such as closures, movable and fixed walls, false roofs, or ceilings, etc., slow down the flow of heat through the fire inhibiting construction, thus also the spread of fire within the building. PA1 Covering the surface of building structures and apparatus which would loose their functionality upon being heated to unduly high temperatures; they slow down the extreme heating of such structures due to their heat insulating capacity. This protection is of great significance in case of structures that support the building e.g. piers, beams, and struts, since they loose their statical stability and load capacity at certain elevated temperatures. PA1 When exposed to fire, at a higher temperature anhydrous salts may chemically attack the material of the structures to be protected. PA1 toxic gases can be formed because of their thermal decomposition PA1 they can cause or accelerate the corrosion of fire inhibiting and protecting structures due to their hygroscopic character PA1 their fire protecting effect decreases with time because of their decrepitation (dehydration), PA1 their volume and morphological habit will alter during the dehydration, PA1 their heat insulating capacity is rather low.
In recent years various methods became known for decreasing structural damage caused by fire. For example, Hungarian Pat. No. 165,720 discloses the use of dicalcium-silicate, sodium silicate, a mixture containing sodium silicate, blowing agent, gas concrete, sludge containing chrome alum earth, and alum earth sludge containing alumina against the spread of fire.
Gas concrete can be advantageously used as a lining structure material in metallurgy because of its heat resistance, but it has not gained wide acceptance in the construction indus try, because it has poor heat insulating qualities. In the case of fire, gas concrete protects the steel structure of buildings against heat only for a short time of several minutes. Then its stability rapidly degrades due to the effect of the heat.
The protective plastering disclosed in Hungarian Pat. No. 163, 497 has a similar disadvantage. It relates to plastering containing mineral additives such as sand, ground rock and/or other minerals, and an organic adhesive, such as latex dispersion, plastic, asphalt or a resin in an aqueous or organic solvent.
Materials with good heat insulating characteristics, such as firebrick, asbestos, rock wool, glass wool, pearlite, guhr, etc., which can be impregnated with water-glass are used for inhibition of the spread of fire. Also foaming paint coatings can be applied onto the surface of the structures to be protected, also containing various inorganic extenders, such as 10 to 15% of clay mineral.
The protecting effect of fire inhibiting materials remains effective only for a short time. From the point of view of effectiveness of fire fighting and minimalizing loss of human life and materials, the time interval of the protective effect is of essential importance.
Since the thickness of insulating layers is limited by constructional considerations, the use of every material is considered as a technical advance the use of an equal thickness of which provides a greater protecting effect against fire than any other material.
Conventional fire inhibiting materials can only be applied to enclose structures to be protected to prevent extreme heating of certain building structures above the critical temperature. The use of such material can be advantageous when filled into existing or created hollow parts within structures to be protected. They also exert protection against fire by another mode of action.
Such fire inhibiting materials can ensure more effective protection against damage which could not be sufficiently realized by conventional insulating materials because of constructional limitations. Generally the protecting effect of structures against the effects of fire was limited, because they have relatively quickly deteriorated in their ability to function according to their purpose.
In a search for materials with heat absorbent characteristics to keep down the heating of supporting elements, experiments were carried out with various salt hydrates that bind water in their crystal structure. Such salt hydrates include Glauber salt and calcium chloride. These materials have a number of drawbacks which render their practical use impossible. These drawbacks include:
Experiments were carried out with hydrophylic silica and with aluminosilicate adsorbents, primarily with zeolites of the A, P and X type. In the experiments asbestos as an insulating material was placed in the outer space of a tubular still made of quartz. A test pot containing the fire protecting materials to be tested was placed in the inner space of the still. The tubular still was heated to 620.degree. C. and the temperature in the middle of the test pot and at the edge thereof was measured as a function of time. The temperature measured at the edge exhibited uniform rise in every experiment, while the tendency of the temperature in the middle of the inner space depended on heat insulating capacity and heat absorption capacity of the material that was examined. The character of the temperature curves of dehydrated zeolites was found to be identical. No measurable difference was found between kaolinite and metakaolinite. On the contrary while testing zeolites the temperature reached a given value only after a comparatively longer time. The delay of temperature rise took place in a temperature range of 1.degree.-350.degree. C.
The measurement was repeated with a test pot being empty on the inside placed in the tubular still and heated to 620.degree. C. The outer space was filled with the material to be examined (asbestos, dehydrated and hydrophylic A-zeolite). The zeolite sample being tested had a particle size of 0.5 to 1.5 mm, and it did not contain any binding material. The temperature curves showed that the heat insulating capacity of dehydrated A-zeolite is slightly superior to that of asbestos, while hydrophylic A-zeolite exhibited essentially higher delay of temperature rise due to its heat insulating capacity and concommitant heat absorbent capacity.